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Antique & Scientific Instruments U.K. |
SOME COMMENTS ON INSTRUMENTS
MADE BY J.B.DANCER, MANCHSTER, ENGLAND
BACKGROUND
My interest in Dancer instruments stems from
my early life in the design and development of scientific instruments. Whereas Dancer
was working at the peak of optical instrument development in the second half of
the 19th century, I was privileged to be treading a similar path a
hundred years later in the age of the silicon chip development. Although I
cannot claim any inventions or discoveries, my work as an electronics design
engineer exposed me to the delights of seeing my new designs in production as
well as the heartache when, despite long hours of unpaid experimentation, an
idea failed to match up to expectations. I should also point out that Dancer's
many elegant solutions to the various problems encountered over the years,
reinforce one of my very first lessons in design. "The best solutions are
always the simplest" That certainly seems to have been the case with
Dancers instruments (How far apart should the lenses on a stereoscopic camera
be? The same distance as a normal pair of eyes of course.).
This together with a very close
geographical link (I was born only a few hundred yards from Cross St.in
Manchester, where he worked some 100 years before I was born) has prompted me
to record my observations on the Dancer instruments that I have had the
privilege to own.
So far, I have collected MICROSCOPES, TELESCOPES,
BAROMETERS, DRAWING
INSTRUMENTS & PHOTOGRAPHIC APARATUS
IS THIS HOW J.B.D. SAW HIS
INSTRUMENTS?
Over the past few years I have been able to study, at
close quarters, several of Dancer's low cost microscopes. All of them have been
signed on the foot with the now famous signature J.B.Dancer Optician Manchester but the
basic instrument (and its case) has developed through several stages to the
comprehensive binocular or set
which any collector would be proud to have.
PRE-1850
The first Dancer microscope I owned was of a good size in a mahogany case with a
drawer full of accessories.
Whilst the instrument was similar in size to
later instruments and had the signed "Y" shaped foot and twin pillar
support, the main focus employed the (earlier) Martin or Drum type microscope rack & pinion focussing internal to the main body
of the instrument. This used only one control knob on the side of the microscope and when the
internal rack had become a little stiff to move, damage to the rack was
inevitable.
The case was of the usual high quality polished mahogany with
substantial lacquered brass handle and held the microscope and free-standing
bullseye condenser in the manner Dancer seemed to favour for the majority of
his microscopes.
The accessory case, however, I have only seen in his early (1840's &
1850's) microscopes. This is a single large drawer with lid mounted on it's
side in the main case, similar the style used by Powel & Leyland and Smith
& Beck on their most expensive microscopes. In this single accessory case
was fitted a stage bullseye condenser, ivory or bone handled spike &
scalpel, tweezers, a live box, stage forceps, 4 objectives (one with Lieberkuhn) all of the pre-RMS thread sizes, a
quantity of slides and a polariser & analyser set. This
accessory set seems to have
employed a particularly neat yet simple storage method using an external thread
on the end of the analyser tube to fix it to a matching internal thread in the
polariser. This saves the necessity for 2 end caps to keep the dust out of the
Nicol prisms, The analyser screws into the
top of an objective before attaching to the microscope. The poleriser slots under the stage on a dovetailed carrier.
The trade label on the
inside of the case door has the address as being 13 Cross St.,
which I would date between 1841 & 1846.
However, I understand Dancer was in partnership with Abrahams form 1841 to
1845, so perhaps this was one of the very first microscopes Dancer made after
the partnership broke up, dating it to 1846. This is how 13
Cross St. looks today.
Early Large Best Microscopes
This large “best” microscope
is from a similar date to the one above but has all the looks of a top of the
range instrument. The twin handled polished mahogany cabinet
holds all the accessories in 2 polished mahogany fitted
drawers with ebony button knobs.
These include a watchmakers eyeglass, polariser/analyser, one top hat style wide
lens eyepiece, camera lucida, fishplate, large overstage, small overstage, 1/8,
½ & 2 inch objectives in matching lacquered brass cans, live box,
compressor stage, wheel of stops, forceps, stage forceps, dark well,
illuminator, micrometer & spanner. A further 7 drawers
are provided for slides and storage of other small items. The rectangular
section limb has a swivel joint to allow the optical
tube to be set outside the area of the stage. Main
focus is by rack & pinion using twin wheels, fine focus
is nose-mounted lever type and the draw tube is
engraved to facilitate setting the tube length for each objective. The
instrument has accessories for both over and under the mechanical stage. Concentric shafts drive the “Y – Y”
movement of the stage by rotating thumbwheels, the fore/aft drive by both left
and right hand knobs. The bayonet mounted mechanical sub-stage
has an achromatic ”illuminator”. All the objectives are pre-RMS and the 1/2 inch has a built-on lieberkuhn. The plano-concave mirror assembly clamps onto the sub-stage tube with a
knurled thumbscrew. The polariser is bayonet fitted below the stage and the analyser screws into the bottom of the draw tube. The fine camera lucida
is a tiny speculum mirror on an arm mounted from the eyepiece and fitted into
it’s own lacquered brass can for storage. The microscope is signed
on the foot Dancer Manchester. The
trade label on the inside of the case door has the address as
being 13 Cross St., which I would date to 1846.
1850'S MICROSCOPE
The next development I had was a similar style of
microscope but housed in the multi-drawer case. This seemed to be the next phase
in case development as small blind holes had been let into the back of the case
door to accommodate
the drawer (ebony?) knobs in a very snug fit. The trade label, now at 43 Cross Street, also had to be moved to the
inside left panel of the case to accommodate these holes. Later cases had
relatively shorter drawers obviating the need for the holes in the door. 43 Cross St. in 2001. I wonder which (if either) of these
buildings was Dancer’s premises?
The objectives still had pre-RMS size threads
and all the accessories found in the single drawer on previous models were
available and fitted in the larger drawers of
this case. The other, smaller drawers were
mostly fitted out to hold slides on end.
It is also interesting to note the
workmanship, which must have been invested in Dancer's free-standing bullseye condenser which came with this set. It was a
substantial piece. The three-dimensional adjustment was clamped with
thumbscrews and the size was in good proportion to the microscope it was to be
used with.
Another, similar microscope of about the same
era came in an identical case except for the absence of the blind holes to
accommodate drawer knobs. The drawers on this model were short enough not to
interfere with case door. This case had also seen better days.
The microscope was similar to the previously
described two with the notable exception of the mechanical stage.
1860'S MICROSCOPE
The development of binocular or stereo vision through
a microscope was tackled in various ways. The most famous of these being the Wenham
prism, almost universally adopted for half a century. Other attempts were made,
including a three part prism assembly by Dancer. Compare this with the Wenham
prism here.
Whereas the Wenham method used a beam
splitting prism to allow binocular vision through a second eye tube “grafted”
onto the side of a monocular microscope body tube, the Dancer method utilised
two body tubes in a true “V” format. Each eyepiece
receives the same amount of light from the objective. The Dancer binocular
prism method was registered No 4380 June 27th
1861.
This particular microscope
came to me without case or accessories. It is a large stand
at about 18 inches high in use, with the Dancer signature
on the heel of the foot. The main focus is rack &
pinion and fine focus by thumbwheel operated nosepiece lever. Inter-ocular
separation is by rack & pinion driven by a thumbwheel either side of the
body tubes. The mechanical stage has a rack & pinion
with thumbwheel both sides for fore & aft movement and a single side worm
driven lateral control. There is a female bayonet fitting for sub-stage
accessories but no accessories present.
The classical twin pillars support the
assembly above the Dancer tri-form base. Unusually the
base has an arc of heavy brass connecting the front two “toes”. Perhaps this
stand began life as a monocular and had to have the extra weight added to the
front of the base for balance when the heavier binocular tubes were fitted.
THE MANCHESTER FIELD
NATURALIST’S BINOCULAR MICROSCOPE
“Manufactured by the desire of the Committee
of the Society” according to Dancer’s
1873 catalogue. The “society” is now the Manchester Microscopical Society (of
which I am a member) and can be found at www.biomed2.man.ac.uk/ns/mm/mms
The microscope is a
portable Wenham binocular instrument which disassembles
to fit into it’s case. It is built on the Ross bar limb style with the Wenham prism mounted in a shoe to slide into the body tube,
which takes the RMS standard objectives and has lots of
unusual features. Apparently it was offered with either
rack & pinion main focus or chain drive. This is
chain driven, presumably to reduce weight. Inter-ocular separation is by a
simple (lightweight) lever mechanism, and the plain stage has a slide bar. The stage has a central hole
threaded to take sub-stage accessories. Below the stage
is a plano-concave mirror. The microscope is signed on the foot “J.B.Dancer
Manchester” and is numbered “26”. Whilst
the inside of the case and drawers are fitted out to take a host of
accessories, sadly the only remaining are a higher power eyepiece and a
nosepiece analyser.
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